Cutting clip = re- render??

Hi,
I'm fairly new to Premiere pro CC, having just switched from FCP7. I have this issue and I wonder if anyone can help.

Hi Have a fairly heavy composite clip, Lots of filters on the keyed clip with animated backgrounds making the render time about an hour. The issue I am having is that I need to trim the starts and ends of the video and add an outro logo.
I can trim all the five video/ image layers and there is no re-rendering required, but if I try to trim the bottom layer (a psd) it will set the entire sequence to red and require re rendering.
I can add a fade to it no problem, I can change layers, no problem. But if i use the razor, or shorten it the entire thing needs to be rendered again.

Very annoying given the amount of time that I have to sit while it renders again.

Premiere Pro with preview render an entire defined area or sequence as a clip, and it does cause one to wonder sometimes just what constitutes sufficient change that the stored render is no longer suitable and a re-render is triggered. It does seem as if trimming usually works fine but any change within the span of a clip itself (trimming/cutting one layer of several that are composited together, etc.) will usually cause the entire clip to require a re-render.

Alex's idea was what I would typically do in these cases...it saves some time.